1. Field of the Invention
This invention is generally directed to dental instruments or tools for repairing teeth and more specifically to a hand-held plier-like instrument for removing crowns from teeth wherein pressure from the instrument may be selectively aligned by a selectively rotatable pin element carried by the tool so as to assure pressure is applied along the elongated axis of teeth during crown removal.
2. History of the Prior Art
In dentistry, it frequently becomes necessary to repair the exterior portion of a patient's tooth with an artificial cover. Such artificial covers are referred to in the art as crowns or caps. In preparing a tooth for a crown, the crown or cap is prepared for placement by initially molding the crown or cap to serve as the exterior of the tooth and to seat properly on a prepared stub. The damaged exterior portions of the tooth are removed leaving a central stub to which the crown or cap will be cemented or adhesively secured.
It sometimes becomes necessary to remove a crown or cap either because the crown or cap has been damaged or because there is some need to work on the tooth which the crown or cap is covering. Special dental tools or instruments have been designed to remove crowns or caps, however, many of these tools have not proven satisfactorily in actual use or their use has resulted in damage to a tooth and/or the crown.
A number of known crown-removing tools utilize a clamping device which engages the crown in an area adjacent the lower rim or margin thereof and which is urged upwardly with respect to a tooth by use of a bolt or screw which is positioned above the tooth and which engages the upper surface of the tooth through a predrilled opening. As the screw or bolt is threaded towards the tooth, the clamping device is elevated thereby urging the crown from the surface of the tooth. Such prior art removal devices have proven to be structurely complicated and difficult to work with especially in the small work area of a patient's mouth. Additionally, the pressure applied by such devices is generally along a central area of the tooth and their use may result in possible damage to the tooth.
In addition to the foregoing, many prior art devices do not permit a great deal of flexibility in use as the relationship of their component parts is generally fixed. Because of this, such devices or tools will cause pressure to be applied in undesired directions with respect to the elongated axis of a tooth thereby causing patient discomfort and possibly causing damage to the crown and/or the tooth. If the set screw used to urge the crown from a tooth is positioned in a fixed relationship with respect to the other portions of a tool used to remove a crown, the application of pressure may be improperly applied. Some examples of prior art crown removal devices include U.S. Pat. Nos. 4,417,876 to Lynch, 3,755,901 to Wilson et al, 1,858,080 to Flagstad et al., and European Pat. No. 0052497, May 1982.
In addition to the foregoing structures for removing crowns or caps, many dentists have attempted to utilize orthodontic tools to remove crowns. A number of orthodontic instruments resemble pliers having specially prepared ends for working orthodontic bands or braces. Some examples of such orthodontic tools include U.S. Pat. Nos. 1,346,584 to Angle, 2,985,962 to Shiner, 3,755,902 to Northcutt, 3,911,583 to Hoffman, 3,986,265 to Cusato, and 4,248,587 to Kurz. Such orthodontic tools have specially prepared jaw portions and the use of such tools to remove crowns or caps, if at all possible, could result in creating undesirable forces or applications of pressure for removing the crown or the cap from a tooth's surface and thereby possibly cause damage to the crown during removal. In addition, if the pressure is improperly applied during the removal process, damage could occur to the pulp of the tooth which is exposed beneath the crown or cap.
Other types of plier-like tools have been specifically designed for removing crowns or caps. In U.S. Pat. No. 3,834,026 to Klein, a pair of crown-removing pliers is disclosed having opposed arcuately shaped jaw surfaces. The tool is utilized by placing the opposing jaw portions in engagement with opposite sides of the crown. The application of pressure at the handles compresses the jaws towards one another to grasp the crown therebetween. Thereafter the crown is removed by moving the pliers either upwardly and downwardly while applying a slight rocking motion. Such rocking motion applies an undesirable pressure against the tooth and can be discomforting to the patient. In addition, the application of pressure toward or perpendicularly to the axis of the root may make removal more difficult. Clamping the crown against the sides of a tooth creates clamping pressure which must be overcome by any vertical pressure applied to remove a crown.
Other prior art plier-like tools used in dentistry utilize jaws having tapered end portions which form points for engaging both the upper and lower portions of a crown. In use of such tools, it has been necessary to apply a rocking motion in order to pull the lower rim of the crown from the surface of the tooth. Again, such rocking motion causes an undesirable application of pressure perpendicularly with respect to the root of a tooth which can create discomfort for the patient. Also, a rocking motion may result in the destruction of the lower rim or margin of the crown.